This application is for 2 years of funding to test relationships between three major domains (host characteristics/influences, venue/event setting characteristics, and participant characteristics) associated with young adult (18-25 years of age) drug use, as well as drug-related and other problems in club settings where electronic music dance events (EMDEs) are held. Subsequently, a competing continuation application will be submitted to test an environmentally based prevention approach in club settings with young adult patrons. Because prevention programs for this age group are mostly limited to college settings, young adults not in college settings are missed. Our preliminary work in club settings have tested our methodologies and yielded findings that support this application. Specifically, we found that 55% of our attendees at EMDEs were not students and recent use (within a 24-hour period) of illegal drugs was 30%, based on our bioassays and self-reports of drug use. Several problems associated with either drug use or with the event were reported by attendees (e.g., driving under the influence, experiencing aggression). The specific aims for this application are (1) to determine the environmental characteristics of venues and events at EMDEs that are associated with drug use, as well as drug-related and other problems; (2) to determine the relationships between characteristics and practices of EMDE hosts (i.e., venue owners, venue managers, event organizers, event promoters) and attendees' drug use, as well as drug-related and other problems; (3) to determine the relationships of attendees' personal characteristics and history of drug use to their levels of drug/alcohol use and their drug use/problems risky behaviors; and (4) to determine the relative contribution of environment, hosts, and participants to drug use, as well as drug-related and other problems. [unreadable] [unreadable] [unreadable]